Methods of producing pre-lithiated silicon oxide electroactive materials comprising silicides and silicates

ABSTRACT

Methods of making a negative electrode material for an electrochemical cell that cycles lithium ions is provided. The method may include centrifugally distributing a molten precursor comprising silicon, oxygen, and lithium by contacting the molten precursor with a rotating surface in a centrifugal atomizing reactor. The molten precursor is formed by combining lithium, silicon, and oxygen. For example, the precursor may be formed from a mixture comprising silicon dioxide (SiO 2 ), lithium oxide (Li 2 O), and silicon (Si). The method may further include solidifying the molten precursor to form a plurality of substantially round solid electroactive particles comprising a mixture of lithium silicide (Li y Si, where 0&lt;y≤4.4) and a lithium silicate (Li 4 SiO 4 ) and having a D50 diameter of less than or equal to about 20 micrometers.

INTRODUCTION

This section provides background information related to the presentdisclosure which is not necessarily prior art.

The present disclosure pertains to methods of forming prelithiatedelectroactive materials for use in negative electrodes of lithium ionelectrochemical cells. The method includes centrifugally distributing amolten precursor comprising silicon, lithium oxide, and optionallysilicon oxide in a centrifugal atomizing reactor that forms aprelithiated silicon oxide material having a mixture of lithium silicideand lithium silicate.

Typical electrochemically active materials for forming anode of negativeelectrode materials for lithium ion electrochemical cells or batteriesinclude lithium-graphite intercalation compounds, lithium-siliconalloying compounds, lithium-tin alloying compounds, and lithium alloys.While graphite compounds are most common, recently, anode materials withhigh specific capacity (in comparison with conventional graphite) are ofgrowing interest. For example, silicon has the highest known theoreticalcharge capacity for lithium, making it one of the most promisingmaterials for rechargeable lithium ion batteries. However, current anodematerials comprising silicon can potentially suffer from significantdrawbacks.

For example, during an initial lithiation and delithation cycle, thesilicon-based electroactive material can undergo excessive volumetricexpansion and contraction. Further, additional volumetric changes mayoccur during successive charging and discharging cycles is observed forsilicon electroactive materials. Such volumetric changes can lead tofatigue cracking and decrepitation of the electroactive material. Thismay potentially lead to a loss of electrical contact between thesilicon-containing electroactive material and the rest of the batterycell as well as the consumption of electrolyte to form new solidelectrolyte interface (SEI), resulting in a decline of electrochemicalcyclic performance, diminished Coulombic charge capacity retention(capacity fade), and limited cycle life. This is especially true atelectrode loading levels required for the application of siliconcontaining electrodes in high-energy lithium ion batteries, such asthose used in transportation applications.

While pre-lithiation of certain silicon based active materials prior toincorporation into the electrochemical cell has been used to minimizesome of these shortcomings, pure lithium and other expensive reactantsare often reactants used for prelithiation. Pure lithium is highlyreactive and thus makes handling more complex during the manufacturingprocess. Accordingly, it would be desirable to develop methods ofprelithiating electroactive materials comprising silicon that can employmore commonly available reactants and can avoid some of the handlingrestrictions that may be required for lithium, while enablingelectroactive materials that are capable of minimal capacity fade andmaximized charge capacity in commercial lithium ion batteries with longlifespans, especially for transportation applications.

SUMMARY

This section provides a general summary of the disclosure, and is not acomprehensive disclosure of its full scope or all of its features.

The present disclosure relates to methods of making a negative electrodematerial for an electrochemical cell that cycles lithium ions. Incertain aspects, the method including centrifugally distributing amolten precursor including silicon, oxygen, and lithium by contactingthe molten precursor with a rotating surface in a centrifugal atomizingreactor. The method also includes solidifying the molten precursor toform a plurality of substantially round solid electroactive particlesincluding a mixture of lithium silicide (Li_(y)Si, where 0<y≤4.4) and alithium silicate (Li₄SiO₄) and having a D50 diameter of less than orequal to about 20 micrometers.

In certain aspects, the molten precursor is formed by melting aprecursor including silicon (Si) and lithium oxide (Li₂O).

In certain further aspects, the precursor includes a mole ratio ofsilicon (Si) to lithium oxide (Li₂O) of greater than or equal to about1:2 to less than or equal to about 2:1.

In certain further aspects, the precursor further includes silicondioxide (SiO₂).

In certain aspects, the lithium silicide is further represented by theformula Li_(4.4x)Si, where x is greater than 0 and less than or equal toabout 0.85.

In certain aspects, the plurality of substantially round solidelectroactive particles include a coating selected from the groupconsisting of: carbon-containing coatings, oxide-containing coatings,and combinations thereof.

In certain aspects, a temperature in the centrifugal atomizing reactoris greater than or equal to 400° C. to less than or equal to about 800°C. during the centrifugally distributing.

In certain aspects, an environment in the centrifugal atomizing reactorhas less than or equal to about 0.5% by weight of any oxygen-bearingspecies.

In certain aspects, a flow rate of the centrifugal atomizing reactor isgreater than or equal to 50 kg/hour to less than or equal to about 500kg/hour.

In certain aspects, the D50 diameter is greater than or equal to about 1μm to less than or equal to about 10 μm.

In certain aspects, the plurality of substantially round solidelectroactive particles has a polydispersity index of less than or equalto about 1.2.

The present disclosure also further relates to a method of making anegative electrode material for an electrochemical cell that cycleslithium ions. The method includes centrifugally distributing a moltenprecursor by contacting the molten precursor with a rotating surface ina centrifugal atomizing reactor. The molten precursor is formed from amixture including silicon dioxide (SiO₂), lithium oxide (Li₂O), andsilicon (Si). The method includes solidifying the molten precursor toform a plurality of substantially round solid electroactive particlesincluding a mixture of lithium silicide (Li_(y)Si, where 0<y≤4.4) and alithium silicate (Li₄SiO₄) and having a D50 diameter of less than orequal to about 20 micrometers.

In certain aspects, the precursor includes a mole ratio of silicon (Si)to lithium oxide (Li₂O) of greater than or equal to about 1:2 to lessthan or equal to about 2:1.

In certain aspects, the lithium silicide is further represented by theformula Li_(4.4x)Si, where x is greater than 0 and less than or equal toabout 0.85.

In certain aspects, a temperature in the centrifugal atomizing reactoris greater than or equal to 400° C. to less than or equal to about 800°C. during the centrifugally distributing.

In certain aspects, a flow rate of the centrifugal atomizing reactor isgreater than or equal to 50 kg/hour to less than or equal to about 500kg/hour.

In certain aspects, the D50 diameter is greater than or equal to about 1μm to less than or equal to about 10 μm.

In certain aspects, the plurality of substantially round solidelectroactive particles has a polydispersity index of less than or equalto about 1.2.

The present disclosure also further relates to a method of making anegative electrode material for an electrochemical cell that cycleslithium ions. The method includes melting a precursor mixture includinglithium oxide (Li₂O) and silicon (Si) to form a molten precursor. Themethod also includes centrifugally distributing the molten precursor bycontacting the molten precursor with a rotating surface in a centrifugalatomizing reactor. The method further includes solidifying the moltenprecursor to form a plurality of substantially round solid electroactiveparticles including lithium silicide (Li_(y)Si, where 0<y≤4.4) and alithium silicate (Li₄SiO₄) and having a D50 diameter of less than orequal to about 20 micrometers.

In certain aspects, the precursor further includes silicon dioxide(SiO₂).

Further areas of applicability will become apparent from the descriptionprovided herein. The description and specific examples in this summaryare intended for purposes of illustration only and are not intended tolimit the scope of the present disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings described herein are for illustrative purposes only ofselected embodiments and not all possible implementations, and are notintended to limit the scope of the present disclosure.

FIG. 1 is a schematic of an example electrochemical battery cell.

FIG. 2 shows an exemplary centrifugal atomizing reactor used inaccordance with the present disclosure to form ultrafine solidelectroactive material particles.

FIG. 3 is an illustration of a cross-sectional view of a negativeelectroactive material particle formed in accordance with certainaspects of the present disclosure, including a lithium-silicon-oxidecomposition forming a negative electroactive particle that can betreated to have a first coating and optionally further treated to have asecond coating.

Corresponding reference numerals indicate corresponding parts throughoutthe several views of the drawings.

DETAILED DESCRIPTION

Example embodiments are provided so that this disclosure will bethorough, and will fully convey the scope to those who are skilled inthe art. Numerous specific details are set forth such as examples ofspecific compositions, components, devices, and methods, to provide athorough understanding of embodiments of the present disclosure. It willbe apparent to those skilled in the art that specific details need notbe employed, that example embodiments may be embodied in many differentforms and that neither should be construed to limit the scope of thedisclosure. In some example embodiments, well-known processes,well-known device structures, and well-known technologies are notdescribed in detail.

The terminology used herein is for the purpose of describing particularexample embodiments only and is not intended to be limiting. As usedherein, the singular forms “a,” “an,” and “the” may be intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. The terms “comprises,” “comprising,” “including,” and“having,” are inclusive and therefore specify the presence of statedfeatures, elements, compositions, steps, integers, operations, and/orcomponents, but do not preclude the presence or addition of one or moreother features, integers, steps, operations, elements, components,and/or groups thereof. Although the open-ended term “comprising,” is tobe understood as a non-restrictive term used to describe and claimvarious embodiments set forth herein, in certain aspects, the term mayalternatively be understood to instead be a more limiting andrestrictive term, such as “consisting of” or “consisting essentiallyof.” Thus, for any given embodiment reciting compositions, materials,components, elements, features, integers, operations, and/or processsteps, the present disclosure also specifically includes embodimentsconsisting of, or consisting essentially of, such recited compositions,materials, components, elements, features, integers, operations, and/orprocess steps. In the case of “consisting of,” the alternativeembodiment excludes any additional compositions, materials, components,elements, features, integers, operations, and/or process steps, while inthe case of “consisting essentially of,” any additional compositions,materials, components, elements, features, integers, operations, and/orprocess steps that materially affect the basic and novel characteristicsare excluded from such an embodiment, but any compositions, materials,components, elements, features, integers, operations, and/or processsteps that do not materially affect the basic and novel characteristicscan be included in the embodiment.

Any method steps, processes, and operations described herein are not tobe construed as necessarily requiring their performance in theparticular order discussed or illustrated, unless specificallyidentified as an order of performance. It is also to be understood thatadditional or alternative steps may be employed, unless otherwiseindicated.

When a component, element, or layer is referred to as being “on,”“engaged to,” “connected to,” or “coupled to” another element or layer,it may be directly on, engaged, connected or coupled to the othercomponent, element, or layer, or intervening elements or layers may bepresent. In contrast, when an element is referred to as being “directlyon,” “directly engaged to,” “directly connected to,” or “directlycoupled to” another element or layer, there may be no interveningelements or layers present. Other words used to describe therelationship between elements should be interpreted in a like fashion(e.g., “between” versus “directly between,” “adjacent” versus “directlyadjacent,” etc.). As used herein, the term “and/or” includes any and allcombinations of one or more of the associated listed items.

Although the terms first, second, third, etc. may be used herein todescribe various steps, elements, components, regions, layers and/orsections, these steps, elements, components, regions, layers and/orsections should not be limited by these terms, unless otherwiseindicated. These terms may be only used to distinguish one step,element, component, region, layer or section from another step, element,component, region, layer or section. Terms such as “first,” “second,”and other numerical terms when used herein do not imply a sequence ororder unless clearly indicated by the context. Thus, a first step,element, component, region, layer or section discussed below could betermed a second step, element, component, region, layer or sectionwithout departing from the teachings of the example embodiments.

Spatially or temporally relative terms, such as “before,” “after,”“inner,” “outer,” “beneath,” “below,” “lower,” “above,” “upper,” and thelike, may be used herein for ease of description to describe one elementor feature's relationship to another element(s) or feature(s) asillustrated in the figures. Spatially or temporally relative terms maybe intended to encompass different orientations of the device or systemin use or operation in addition to the orientation depicted in thefigures.

Throughout this disclosure, the numerical values represent approximatemeasures or limits to ranges to encompass minor deviations from thegiven values and embodiments having about the value mentioned as well asthose having exactly the value mentioned. Other than in the workingexamples provided at the end of the detailed description, all numericalvalues of parameters (e.g., of quantities or conditions) in thisspecification, including the appended claims, are to be understood asbeing modified in all instances by the term “about” whether or not“about” actually appears before the numerical value. “About” indicatesthat the stated numerical value allows some slight imprecision (withsome approach to exactness in the value; approximately or reasonablyclose to the value; nearly). If the imprecision provided by “about” isnot otherwise understood in the art with this ordinary meaning, then“about” as used herein indicates at least variations that may arise fromordinary methods of measuring and using such parameters. For example,“about” may comprise a variation of less than or equal to 5%, optionallyless than or equal to 4%, optionally less than or equal to 3%,optionally less than or equal to 2%, optionally less than or equal to1%, optionally less than or equal to 0.5%, and in certain aspects,optionally less than or equal to 0.1%.

In addition, disclosure of ranges includes disclosure of all values andfurther divided ranges within the entire range, including endpoints andsub-ranges given for the ranges.

As used herein, the terms “composition” and “material” are usedinterchangeably to refer broadly to a substance containing at least thepreferred chemical constituents, elements, or compounds, but which mayalso comprise additional elements, compounds, or substances, includingtrace amounts of impurities, unless otherwise indicated.

Example embodiments will now be described more fully with reference tothe accompanying drawings.

The present technology pertains to improved electroactive materials forelectrochemical cells, especially lithium-ion batteries. In variousinstances, such cells are used in vehicle or automotive transportationapplications (e.g., motorcycles, boats, tractors, buses, motorcycles,mobile homes, campers, and tanks). However, the present technology maybe employed in a wide variety of other industries and applications,including aerospace components, consumer goods, devices, buildings(e.g., houses, offices, sheds, and warehouses), office equipment andfurniture, and industrial equipment machinery, agricultural or farmequipment, or heavy machinery, by way of non-limiting example. Incertain aspects, the lithium ion batteries can be used in a variety ofconsumer products and vehicles, such as Hybrid Electric Vehicles (HEVs)and Electric Vehicles (EVs).

An exemplary illustration of an electrochemical cell or battery forcycling lithium ions is shown in FIG. 1 . The battery 20 includes anegative electrode 22, a positive electrode 24, and a separator 26(e.g., a microporous polymeric separator) disposed between the twoelectrodes 22, 24. The separator 26 comprises an electrolyte 30, whichmay also be present in the negative electrode 22 and positive electrode24. A negative electrode current collector 32 may be positioned at ornear the negative electrode, 22 and a positive electrode currentcollector 34 may be positioned at or near the positive electrode 24. Aninterruptible external circuit 40 and load device 42 connects thenegative electrode 22 (through its current collector 32) and thepositive electrode 24 (through its current collector 34).

The battery 20 can generate an electric current during discharge by wayof reversible electrochemical reactions that occur when the externalcircuit 40 is closed (to connect the negative electrode 22 and thepositive electrode 24) and the negative electrode 22 has a lowerpotential than the positive electrode. The chemical potential differencebetween the positive electrode 24 and the negative electrode 22 driveselectrons produced by a reaction, for example, the oxidation ofintercalated lithium, at the negative electrode 22 through the externalcircuit 40 towards the positive electrode 24. Lithium ions that are alsoproduced at the negative electrode 22 are concurrently transferredthrough the electrolyte 30 contained in the separator 26 towards thepositive electrode 24. The electrons flow through the external circuit40 and the lithium ions migrate across the separator 26 containing theelectrolyte solution 30 to form intercalated lithium at the positiveelectrode 24. As noted above, electrolyte 30 is typically also presentin the negative electrode 22 and positive electrode 24. The electriccurrent passing through the external circuit 40 can be harnessed anddirected through the load device 42 until the lithium in the negativeelectrode 22 is depleted and the capacity of the battery 20 isdiminished.

The battery 20 can be charged or re-energized at any time by connectingan external power source to the lithium ion battery 20 to reverse theelectrochemical reactions that occur during battery discharge.Connecting an external electrical energy source to the battery 20promotes a reaction, for example, non-spontaneous oxidation ofintercalated lithium, at the positive electrode 24 so that electrons andlithium ions are produced. The lithium ions flow back towards thenegative electrode 22 through the electrolyte 30 across the separator 26to replenish the negative electrode 22 with lithium (e.g., intercalatedlithium) for use during the next battery discharge event. As such, acomplete discharging event followed by a complete charging event isconsidered to be a cycle, where lithium ions are cycled between thepositive electrode 24 and the negative electrode 22. The external powersource that may be used to charge the battery 20 may vary depending onthe size, construction, and particular end-use of the battery 20. Somenotable and exemplary external power sources include, but are notlimited to, an AC-DC converter connected to an AC electrical power gridthough a wall outlet and a motor vehicle alternator.

In many lithium-ion battery configurations, each of the negativeelectrode current collector 32, negative electrode 22, the separator 26,positive electrode 24, and positive electrode current collector 34 areprepared as relatively thin layers (for example, from several microns toa fraction of a millimeter or less in thickness) and assembled in layersconnected in electrical parallel arrangement to provide a suitableelectrical energy and power package. The negative electrode currentcollector 32 and positive electrode current collector 34 respectivelycollect and move free electrons to and from an external circuit 40.

Further, the separator 26 operates as an electrical insulator by beingsandwiched between the negative electrode 22 and the positive electrode24 to prevent physical contact and thus, the occurrence of a shortcircuit. The separator 26 provides not only a physical and electricalbarrier between the two electrodes 22, 24, but also contains theelectrolyte solution in a network of open pores during the cycling oflithium ions, to facilitate functioning of the battery 20.

Furthermore, the battery 20 can include a variety of other componentsthat while not depicted here are nonetheless known to those of skill inthe art. For instance, the battery 20 may include a casing, gaskets,terminal caps, tabs, battery terminals, and any other conventionalcomponents or materials that may be situated within the battery 20,including between or around the negative electrode 22, the positiveelectrode 24, and/or the separator 26. The battery 20 described aboveincludes a liquid electrolyte and shows representative concepts ofbattery operation. However, the battery 20 may also be a solid-statebattery that includes a solid-state electrolyte that may have adifferent design, as known to those of skill in the art.

As noted above, the size and shape of the battery 20 may vary dependingon the particular application for which it is designed. Battery-poweredvehicles and hand-held consumer electronic devices, for example, are twoexamples where the battery 20 would most likely be designed to differentsize, capacity, and power-output specifications. The battery 20 may alsobe connected in series or parallel with other similar lithium-ion cellsor batteries to produce a greater voltage output, energy, and power ifit is required by the load device 42. Accordingly, the battery 20 cangenerate electric current to a load device 42 that is part of theexternal circuit 40. The load device 42 may be powered by the electriccurrent passing through the external circuit 40 when the battery 20 isdischarging. While the electrical load device 42 may be any number ofknown electrically-powered devices, a few specific examples include anelectric motor for an electrified vehicle, a laptop computer, a tabletcomputer, a cellular phone, and cordless power tools or appliances. Theload device 42 may also be an electricity-generating apparatus thatcharges the battery 20 for purposes of storing electrical energy.

With renewed reference to FIG. 1 , the positive electrode 24, thenegative electrode 22, and the separator 26 may each include anelectrolyte solution or system 30 inside their pores, capable ofconducting lithium ions between the negative electrode 22 and thepositive electrode 24. Any appropriate electrolyte 30, whether in solid,liquid, or gel form, capable of conducting lithium ions between thenegative electrode 22 and the positive electrode 24 may be used in thelithium-ion battery 20. In certain aspects, the electrolyte 30 may be anon-aqueous liquid electrolyte solution that includes a lithium saltdissolved in an organic solvent or a mixture of organic solvents.Numerous conventional non-aqueous liquid electrolyte 30 solutions may beemployed in the lithium-ion battery 20.

In certain aspects, the electrolyte 30 may be a non-aqueous liquidelectrolyte solution that includes one or more lithium salts dissolvedin an organic solvent or a mixture of organic solvents. Numerous aproticnon-aqueous liquid electrolyte solutions may be employed in thelithium-ion battery 20. For example, a non-limiting list of lithiumsalts that may be dissolved in an organic solvent to form thenon-aqueous liquid electrolyte solution include lithiumhexafluorophosphate (LiPF₆), lithium perchlorate (LiClO₄), lithiumtetrachloroaluminate (LiAlCl₄), lithium iodide (LiI), lithium bromide(LiBr), lithium thiocyanate (LiSCN), lithium tetrafluoroborate (LiBF₄),lithium tetraphenylborate (LiB(C₆H₅)₄), lithium bis(oxalato)borate(LiB(C₂O₄)₂) (LiBOB), lithium difluorooxalatoborate (LiBF₂(C₂O₄)),lithium hexafluoroarsenate (LiAsF₆), lithium trifluoromethanesulfonate(LiCF₃SO₃), lithium bis(trifluoromethane)sulfonylimide (LiN(CF₃SO₂)₂),lithium bis(fluorosulfonyl)imide (LiN(FSO₂)₂) (LiSFI), and combinationsthereof.

These and other similar lithium salts may be dissolved in a variety ofaprotic organic solvents, including but not limited to, various alkylcarbonates, such as cyclic carbonates (e.g., ethylene carbonate (EC),propylene carbonate (PC), butylene carbonate (BC), fluoroethylenecarbonate (FEC)), linear carbonates (e.g., dimethyl carbonate (DMC),diethyl carbonate (DEC), ethylmethylcarbonate (EMC)), aliphaticcarboxylic esters (e.g., methyl formate, methyl acetate, methylpropionate), γ-lactones (e.g., γ-butyrolactone, γ-valerolactone), chainstructure ethers (e.g., 1,2-dimethoxyethane, 1-2-diethoxyethane,ethoxymethoxyethane), cyclic ethers (e.g., tetrahydrofuran,2-methyltetrahydrofuran), 1,3-dioxolane), sulfur compounds (e.g.,sulfolane), and combinations thereof.

The porous separator 26 may include, in certain instances, a microporouspolymeric separator including a polyolefin. The polyolefin may be ahomopolymer (derived from a single monomer constituent) or aheteropolymer (derived from more than one monomer constituent), whichmay be either linear or branched. If a heteropolymer is derived from twomonomer constituents, the polyolefin may assume any copolymer chainarrangement, including those of a block copolymer or a random copolymer.Similarly, if the polyolefin is a heteropolymer derived from more thantwo monomer constituents, it may likewise be a block copolymer or arandom copolymer. In certain aspects, the polyolefin may be polyethylene(PE), polypropylene (PP), or a blend of PE and PP, or multi-layeredstructured porous films of PE and/or PP. Commercially availablepolyolefin porous separator membranes 26 include CELGARD® 2500 (amonolayer polypropylene separator) and CELGARD® 2320 (a trilayerpolypropylene/polyethylene/polypropylene separator) available fromCelgard LLC.

In certain aspects, the separator 26 may further include one or more ofa ceramic coating layer and a heat-resistant material coating. Theceramic coating layer and/or the heat-resistant material coating may bedisposed on one or more sides of the separator 26. The material formingthe ceramic layer may be selected from the group consisting of: alumina(Al₂O₃), silica (SiO₂), and combinations thereof. The heat-resistantmaterial may be selected from the group consisting of: Nomex, Aramid,and combinations thereof.

When the separator 26 is a microporous polymeric separator, it may be asingle layer or a multi-layer laminate, which may be fabricated fromeither a dry or a wet process. For example, in certain instances, asingle layer of the polyolefin may form the entire separator 26. Inother aspects, the separator 26 may be a fibrous membrane having anabundance of pores extending between the opposing surfaces and may havean average thickness of less than a millimeter, for example. As anotherexample, however, multiple discrete layers of similar or dissimilarpolyolefins may be assembled to form the microporous polymer separator26. The separator 26 may also comprise other polymers in addition to thepolyolefin such as, but not limited to, polyethylene terephthalate(PET), polyvinylidene fluoride (PVdF), a polyamide, polyimide,poly(amide-imide) copolymer, polyetherimide, and/or cellulose, or anyother material suitable for creating the required porous structure. Thepolyolefin layer, and any other optional polymer layers, may further beincluded in the separator 26 as a fibrous layer to help provide theseparator 26 with appropriate structural and porosity characteristics.In certain aspects, the separator 26 may also be mixed with a ceramicmaterial or its surface may be coated in a ceramic material. Forexample, a ceramic coating may include alumina (Al₂O₃), silicon dioxide(SiO₂), titania (TiO₂) or combinations thereof. Various conventionallyavailable polymers and commercial products for forming the separator 26are contemplated, as well as the many manufacturing methods that may beemployed to produce such a microporous polymer separator 26.

In various aspects, the porous separator 26 and the electrolyte 30 maybe replaced with a solid-state electrolyte (SSE) (not shown) thatfunctions as both an electrolyte and a separator. The SSE may bedisposed between the positive electrode 24 and negative electrode 22.The SSE facilitates transfer of lithium ions, while mechanicallyseparating and providing electrical insulation between the negative andpositive electrodes 22, 24. By way of non-limiting example, SSEs mayinclude LiTi₂(PO₄)₃, LiGe₂(PO₄)₃, Li₇La₃Zr₂O₁₂, Li₃xLa_(2/3)-xTiO₃,Li₃PO₄, Li₃N, Li₄GeS₄, Li₁₀GeP₂S₁₂, Li₂S—P₂S₅, Li₆PS₅Cl, Li₆PS₅Br,Li₆PS₅I, Li₃OCl, Li_(2.99) Ba_(0.005)ClO, or combinations thereof.

The positive electrode 24 may be formed from a lithium-based activematerial that can sufficiently undergo lithium intercalation anddeintercalation, or alloying and dealloying, while functioning as thepositive terminal of the battery 20. One exemplary common class of knownmaterials that can be used to form the positive electrode 24 is layeredlithium transitional metal oxides. For example, in certain aspects, thepositive electrode 24 may comprise one or more materials having a spinelstructure, such as lithium manganese oxide (Li_((1+x))Mn₂O₄, where0.1≤x≤1),-lithium manganese nickel oxide (LiMn_((2−x))Ni_(x)O₄, where0≤x≤0.5) (e.g., LiMn_(1.5)Ni_(0.5)O₄); one or more materials with alayered structure, such as lithium cobalt oxide (LiCoO₂), lithium nickelmanganese cobalt oxide (Li(Ni_(x)Mn_(y)Co_(z))O₂, where 0≤x≤1, 0≤y≤1,0≤z≤1, and x+y+z=1) (e.g., LiMn_(0.33)Ni_(0.33)Co_(0.)33O2), or alithium nickel cobalt metal oxide (LiNi_((1−x−y))Co_(x)M_(y)O₂, where0<x<0.2, y<0.2, and M may be Al, Mg, Ti, or the like); or a lithium ironpolyanion oxide with olivine structure, such as lithium iron phosphate(LiFePO₄), lithium manganese-iron phosphate (LiMn_(2-x)Fe_(x)PO₄, where0<x<0.3), or lithium iron fluorophosphate (Li₂FePO₄F).

In certain variations, the positive electroactive materials may beintermingled with an electronically conducting material that provides anelectron conduction path and/or at least one polymeric binder materialthat improves the structural integrity of the electrode. For example,the electroactive materials and electronically or electricallyconducting materials may be slurry cast with such binders, likepolyvinylidene difluoride (PVdF), polytetrafluoroethylene (PTFE),ethylene propylene diene monomer (EPDM) rubber, or carboxymethylcellulose (CMC), a nitrile butadiene rubber (NBR), styrene-butadienerubber (SBR), lithium polyacrylate (LiPAA), sodium polyacrylate (NaPAA),sodium alginate, lithium alginate. Electrically conducting materials mayinclude carbon-based materials, powdered nickel or other metalparticles, or a conductive polymer. Carbon-based materials may include,for example, particles of graphite, acetylene black (such as KETCHEN™black or DENKA™ black), carbon fibers and nanotubes, graphene, and thelike. Examples of a conductive polymer include polyaniline,polythiophene, polyacetylene, polypyrrole, and the like. In certainaspects, mixtures of the conductive materials may be used. The positiveelectrode current collector 34 may be formed from aluminum (Al) or anyother appropriate electrically conductive material known to those ofskill in the art.

The negative electrode 22 includes an electroactive material as alithium host material capable of functioning as a negative terminal of alithium ion battery. The negative electrode current collector 32 maycomprise a metal comprising copper, nickel, or alloys thereof or otherappropriate electrically conductive materials known to those of skill inthe art. In certain aspects, the positive electrode current collector 34and/or negative electrode current collector 32 may be in the form of afoil, slit mesh, and/or woven mesh.

In certain aspects, the present disclosure provides methods of makingnegative electrodes 22 (e.g., anodes) that incorporate improvedelectrochemically active negative electrode materials. As discussedabove, the negative electroactive materials suffer from significantvolumetric expansion during lithium cycling (e.g., capable of acceptingthe insertion of lithium ions during charging of the electrochemicalcell via lithiation or “intercalation” and releasing lithium ions duringdischarging of the electrochemical cell via delithiation or“deintercalation” or lithium alloying/dealloying). Such anelectrochemically active negative electrode material may be selectedfrom the group consisting of: silicon, silicon-containing alloys,graphite, and combinations thereof. By way of example, electroactivematerial particles comprising silicon may include silicon, or siliconcontaining binary and ternary alloys. In accordance with various aspectsof the present teachings, a negative electroactive material can beincorporated into a negative electrode in an electrochemical cell.

Furthermore, in a typical manufacturing process, a negative electrodematerial is incorporated into the electrochemical cell without anylithium. The positive electrode has lithium and after cycling theelectrochemical cell, lithium passes into and lithiates the negativeelectrode. However, in negative electroactive materials includingsilicon, for example, a portion of the lithium may not cycle backthrough the electrolyte to the positive electrode, but instead mayremain with the negative electrode following the first lithiation cycle.This may be due to for example, formation of lithium silicates, such asLi₄SiO₄ and/or a solid electrolyte interphase (SEI) layer on thenegative electrode, as well as ongoing lithium loss due to continuoussolid electrolyte interphase (SEI) breakage. The solid electrolyteinterface (SEI) layer can form over the surface of the negativeelectrode (anode), which is often generated by reaction products ofanode material, electrolyte reduction, and/or lithium ion reduction.Such permanent loss of lithium ions may result in a decreased specificenergy and power in the battery resulting from added positive electrodemass that does not participate in the reversible operation of thebattery. For example, the lithium-ion battery may experience anirreversible capacity loss of greater than or equal to about 5% to lessthan or equal to about 30% after the first cycle.

Lithiation, for example pre-lithiation of the electroactive materialsprior to incorporation into an electrochemical cell, may compensate forsuch lithium losses during cycling. Common lithiation methods, such aselectrochemical, direct contact, and lamination methods; however, oftenrequire half-cell fabrication and teardown and/or high temperaturechemical processes. Furthermore, it can be difficult to control anextent of lithiation that occurs during these processes. Further, theseprocesses involve highly reactive chemicals and require additionalmanufacturing steps. These may be time consuming and potentiallyexpensive processes. Further, such processes also commonly produceunworkable materials, for example anodes having undesirable thicknesses.

The present disclosure provides improved electroactive and electrodematerials, and methods of making the same, which can address thesechallenges. In various aspects, the present disclosure providesadvantages, including reducing mechanical stress in negative electrodesby forming pre-lithiated negative electroactive materials comprisingsilicon prior to forming the electrode. Notably, the electroactivematerials are both formed and pre-lithiated in a single process.Further, the active lithium loss during formation cycles can besignificantly reduced by the present technology. Additionally, cyclelife performance of lithium ion batteries incorporating negativeelectrodes with negative electroactive materials comprisingpre-lithiated silicon is improved in accordance with certain aspects ofthe present disclosure.

Prelithiation of reactant materials via centrifugal atomization can beconducted by lithiation of silicon by a reaction expressed by:4.4xLi+Si→Li_(4.4x)Si, where 0<x≤1. This prelithiation process may userelatively pure lithium (Li) metal and silicon (Si) as reactants.However, lithium metal is highly reactive and requires special handlingand safety precautions. Moreover, while the product of such a reactionis lithium silicide (Li_(4.4x)Si, where 0<x≤1) that is an electroactivematerial that is prelithiated, it still may undergo significantvolumetric expansion during lithium cycling that occurs within batteryoperation.

Thus, in accordance with certain aspects of the present disclosure,methods are provided for making an electroactive material for a negativeelectrode of an electrochemical cell that cycles lithium ions, asdescribed above. The method may be a process for creating pre-lithiatedelectroactive material particles, like lithiated silicon oxide alloys.The precursors for forming the lithiated silicon-containingelectroactive materials include lithium, silicon, and oxygen. In certainvariations, the precursor may be formed by combining lithium oxide(Li₂O) and silicon (Si). In certain other variations, the precursor maybe formed by combining lithium oxide (Li₂O), silicon (Si), andoptionally silicon dioxide or silica (SiO₂). These starting materialsare more widely available and thus less expensive than pure lithium (Li)metal. Further, the manufacturing process requires fewer safetyprecautions in avoiding handling of pure lithium metal as a reactant,which is highly reactive.

Generally, production of lithium silicide (Li_(y)Si) and lithiumsilicate (Li₄SiO₄) may occur by a thermochemical reduction that involvesthe following reactions in Equations (1)-(3):2Li₂O+Si=4Li+SiO₂  (1)yLi+Si=Li_(y)Si(silicide), where 0<y≤4.4  (2)2Li₂O+SiO₂═Li₄SiO₄(silicate)  (3)The heat of formation of Li₂O is about (−600 kJ/mol) and SiO₂ (−910KJ/mol).

Thus, starting from Li₂O, Si, and/or SiO₂ reactant materials, athermochemical reaction is conducted that forms prelithiated siliconoxide (SiO_(x)) particles that comprise both electroactive lithiumsilicides (e.g., Li_(y)Si, where 0<y≤4.4, for example, in certainvariations, Li_(4.4x)Si, where 0<x≤about 0.85) and inactive lithiumsilicates. Lithium silicates may include Li₄SiO₄, Li₈SiO₆, Li₂SiO₃, andLi₂Si₂O₅. In certain aspects, the lithium silicate(s) formed in thethermochemical reaction may be represented by Li₄SiO₄, which is believedto be the dominant and most stable lithium silicate (having highestmelting point), although as appreciated by those of skill in the art mayinclude other lithium silicates in the final product. Notably, as shownin Equation (4), for a silicon oxide (SiO) product that is lithiated,part of the lithiation reaction of silicon oxide is reversible(formation of the electroactive lithium silicide), while part of thesituation reaction that occurs is irreversible (formation of the lithiumsilicate).SiO+4Li→0.75Li₄Si(reversible)+0.25Li₄SiO₄(irreversible)  (4)

Thus, when silicon oxide based electroactive materials are incorporatedinto an electrochemical cell, lithium (Li) consumption may occur duringcycling by formation of the lithium silicate (Li₄SiO₄) and/or formationof the SEI layer on a surface of the electroactive material. However,where the silicon oxide material is prelithiated in accordance withcertain aspects of the present teachings, it reduces consumption oflithium during initial cycling of the cell by having already formed theirreversible lithium silicate product. Notably, the silicon-oxidecontaining product formed in accordance with certain aspects of thepresent disclosure may have a predetermined amount of electrochemicallyinert lithium silicate combined with electroactive lithium silicide.

However, the presence lithium silicate (mixed with the lithium silicide)in the electroactive material particles can provide certain advantagesto the electroactive material, for example, enhancing mechanicalstrength and reducing volumetric expansion changes that may occur duringlithiation and prelithiation to reduce stress on the electroactivematerials during cycling and thus reduce the potential for cracking,decrepitation, and the like. Thus, the silicon-oxide containing productscomprising both lithium silicide and lithium silicates are more robustthan a comparable electroactive material that predominantly containslithium silicide alone.

In certain aspects, a silicon oxide final product includes a lithiumsilicate, which may be represented by Li₄SiO₄ where a ratio of Li/Si isabout 4 (e.g., 4:1), and a lithium silicide, Li_(4.4y)Si, where a ratioof Li/Si is greater than 0 to about 4.4. Thus, an overall ratio of Li/Simay range from greater than 0 to about 4.4. For a precursor includingLi₂O and Si, a ratio of Li₂O/Si may range from greater than 0 to about2.2. In certain non-limiting aspects, a mole ratio of the lithium oxide(Li₂O) to silicon (Si) in a precursor may be about 2:1 to about 1:2 (6moles of excess Si) when using silicon (Si) to control the constituentsof the final product. In alternative aspects, lithium oxide (Li₂O) andsilicon oxide (SiO₂) may be used to control the constituents of thefinal product.

These pre-lithiated electroactive material particles may further haveone or more coatings applied thereon, such as a carbonaceous coatingand/or an oxide-based coating, described in U.S. Patent Publication No.2021/0175491 entitled “Methods of Forming Prelithiated Silicon AlloyElectroactive Materials,” the relevant portions of which areincorporated herein by reference. These oxide-based coatings maycomprise aluminum oxide (Al₂O₃), titanium oxide coating (TiO₂), vanadiumpentoxide coating (V₂O₅), zirconium oxide coating (ZrO₂), hafnium oxide(HfO₂), zinc oxide coating (ZnO), silicon oxide (SiO₂), and combinationsthereof. The coating may comprise an electrically conductive andionically conductive layer that comprises a carbon-containing orcarbonaceous material. In certain aspects, the electrically conductiveand ionically conductive layer may comprise an amorphous carbon thatgenerally lacks any crystalline structure or ordering or graphiticcarbon. As will be described herein, the process may be performed viacentrifugal/gas atomization that forms prelithiated SiO_(x) particleshaving an advantageous substantially spherical shape with a narrow sizedistribution range. Further, compared to other pre-lithiation methods,centrifugal/gas atomization is a high production rate process thatprovides a means to precisely control pre-lithiation levels and thephases formed in the product. Thus, a unique spherical compositestructure is created that can stabilize the prelithiated silicon oxides(SiO_(x)) product and attain desired mechanical and electrochemicalperformance when used as a battery anode material.

In various aspects, the present disclosure provides controllable phaseratios in the final product. For example, phase ratios are controllablevia controlling the relative amounts of starting materials, such asratios of lithium oxide (Li₂O) and silicon provided in silicon metal(Si) or silicon dioxide (SiO₂). The final product of prelithiatedsilicon oxides (SiO_(x)) include a first component of silicide (e.g.,Li_(y)Si) and a second component of silicate (e.g., Li₄SiO₄). In certainaspects, a stoichiometric ratio of lithium silicides (e.g., Li_(y)Si,where 0<y≤4.4) and inactive lithium silicates (e.g., Li₄SiO₄) formed inthe product may be about 1:1 to about 3:1.

Thus, the present disclosure contemplates improving battery cycle lifeperformance. Further, the present disclosure mitigates potential safetyconcerns in the manufacturing process that would otherwise occur iflithium metal was employed as a reactant for prelithiation. Further, themanufacturing process helps reduce raw material costs.

The present disclosure contemplates a method of making lithiated siliconelectroactive materials from precursors comprising silicon, oxygen, andlithium by a centrifugal/gas atomization process. In centrifugalatomization processing, a molten material is directed towards at leastone rotating disc or cup, where melt drops form and fly away from therotating disc or cup to solidify and form spherical particle siliconoxides. Thus, in certain aspects, a method of making a negativeelectrode material for an electrochemical cell that cycles lithium ionsis provided. The method comprises centrifugally distributing a moltenprecursor comprising silicon, lithium, and oxygen by contacting themolten precursor with a rotating surface in a centrifugal atomizingreactor and solidifying the molten precursor to form a plurality ofsubstantially round solid electroactive particles comprising an alloy oflithium and silicon and having a D50 diameter of less than or equal toabout 20 micrometers. In certain variations, the centrifugal atomizationprocess forms a plurality of particles having a relatively smallparticle size (e.g., ultrafine particles) with a smaller particle sizedistribution (e.g., monodisperse).

FIG. 2 shows an exemplary centrifugal atomizing reactor 50. It should benoted that the reactor 50 is a simplified version and may containvarious other equipment. One suitable multistage centrifugal atomizingreactor suitable for forming the plurality of electroactive particles isdescribed in U.S. Patent Publication No. 2021/0138548 entitled “Articlefor Producing Ultra-Fine Powders and Method of Manufacture Thereof,” therelevant portions of which are incorporated herein by reference. Amolten precursor material 60 can be conveyed in batches or continuouslyfrom an upstream furnace and introduced to a distribution vessel ortundish 62. The tundish 62 has at least one outlet port 64 with asuitable diameter to facilitate a quick discharge of the moltenprecursor material 60. The number and the diameter of the outlet ports64 may be adjusted to control particle size during and after atomizationprocess, as appreciated by those of skill in the art. Further, thetundish 62 may rotate or have a source of pressure to enhance dischargevia the outlet port 64. A stream 66 of molten precursor material 60 isdischarged from the outlet port 64.

The stream 66 contacts a surface 76 of a rotating component 70 that maybe in the form of a disc or cup. The rotating component 70 is in rotarycommunication with a shaft 72 and a motor 74. Rotary motion istransmitted from the motor 74 via the shaft 72 to the rotating component70. The rotary motion of the rotating component 70 imparts a centrifugalforce to the molten precursor material 60, which causes it to distributeand comminute the precursor material in a centrifugal direction 78 inthe reactor 50 outwards from the central axis defined by the shaft 72.As shown, the molten precursor material 60 contacts the rotating surface76 and as it passes in an outward direction creates droplets 80 thatsolidify to form a plurality of substantially round solid electroactiveparticles 82. While not shown, ultrasonic or mechanical vibration may beapplied to the rotating component 70 to facilitate comminution of themolten material as well as de-agglomeration of particles. The droplets80 are thrust outward. The solid particles 82 are outwardly thrusttowards a wall 84 of the reactor 50 and then fall into an outlet region86 that includes an outlet 88. The ultrafine solid particles 82 aretransported by gravity to the outlet 88. As shown, a collection vessel90 is connected to the outlet 88 and collects the particles 82; however,as will be described in detail below, the outlet 88 alternatively may bein fluid communication with additional reactor chambers.

The solidified particles formed by such a process may be relativelysmall (e.g., fine or ultrafine) and have a substantially round shape.“Substantially round-shaped” includes particles having low aspect ratiosand with a morphology or shape including spherical, orbed, spheroidal,egg-shaped, elliptical, and the like. In certain variations, theparticles have a spherical shape. Further, the solid particles may havean average diameter (D). A D50 means a cumulative 50% point of diameter(or 50% pass particle size) for the plurality of solid particles. Incertain aspects, the D50 of the plurality of electroactive solidparticles formed by a centrifugal atomization process is less than orequal to about 20 micrometers, optionally less than or equal to about 15micrometers, optionally less than or equal to about 10 micrometers, andoptionally less than or equal to about 5 micrometers. In certainvariations, the D50 for the plurality of solid electroactive particlesformed may be greater than or equal to about 1 μm to less than or equalto about 20 μm, optionally greater than or equal to about 1 μm to lessthan or equal to about 10 μm.

The plurality of electroactive solid particles formed by a centrifugalatomization process may be relatively monodisperse, for example, havinga narrow polydispersity index or variation in particle sizes among theplurality of particles formed. In one aspect, the particle distributionis narrow having a polydispersity index of less than or equal to about1.2, for example.

In certain aspects, the centrifugal atomization process of forming theplurality of electroactive materials may provide a high yield for thetarget or predetermined particle size diameter range. For example, wherean average particle diameter is selected to be greater than or equal toabout 1 μm to less than or equal to about 20 μm, an overall yield fromthe process for solid particles having the predetermined size range maybe greater than or equal to about 10% to less than or equal to about90%. These uniform diameter electroactive materials formed from an alloyof lithium and silicon may be used in various electrochemicalcells/batteries and energy storage devices.

In certain variations, an environment in the centrifugal atomizingreactor may be substantially free of gaseous oxygen-containing speciesto avoid reaction with lithium. While lithium is not added as aprecursor/reactant, it may form as an intermediate and thus as aprecaution, the environment in which the reactions occur may berelatively inert. For example, the environment may have less than orequal to about 0.5% by weight of any oxygen-bearing species in a gasphase, for example, oxygen gas, water, and the like. The environment inthe reactor optionally has a low water/moisture level reflected by arelative humidity (RH) of less than or 0.5% at reaction conditiontemperatures.

The centrifugal atomizing reactor may be capable of high throughput, forexample, having a mass flow rate of greater than or equal to 50 kg/hourto less than or equal to about 500 kg/hour in forming the particles ofelectroactive materials with the desired range of average particlesizes. Higher flow rates may also be possible, so long as the particlesformed have the desired D50. The flow rate has an effect on particlesize. For example, the higher the flow rate of the molten material, thelarger size of the particles that are produced. So the flow rate may belimited by the desired size of the particles.

Furthermore, the methods provided by certain aspects of the presentdisclosure advantageously provide a high level of control over thecompositions of the electroactive materials formed. The methods of thepresent disclosure provide an ability to directly manufacture apre-lithiated electroactive material comprising silicon, without theneed for an initial formation step for the particle followed by apre-lithiation step where lithium is introduced to the material. Asnoted above, the alloy comprising lithium and silicon that is formed bythe present methods may be represented by the formula: lithium silicide(Li_(y)Si, where 0<y≤4.4) or in certain variations, Li_(4.4x)Si, where0<x≤about 0.85. The precursor material for forming the electro activematerial alloy can be selected to have specific compositions that mayform specific phases, depending on the temperature conditions selectedduring the centrifugal atomizing process in the reactor. Thus, precisecontrol of the phases present in the particles formed can be attainedthrough the composition of the melt.

In certain aspects, the precursor material has sufficient amounts ofoxygen and lithium in combination with silicon to fully form the lithiumsilicate phase (Li₄SiO₄) phase. Additional amounts of lithium can bevaried to form different variations of the Li—Si phase. As will beappreciated by those of skill in the art, it can be desirable tomaximize a relative stoichiometric amount of lithium in thelithium-silicon alloy/electroactive material. In certain aspects, theprecursor material is selected to have greater than 0 atomic % to lessthan or equal to about 82 at. % of lithium and correspondingly greaterthan or equal to about 18 atomic % to less than or equal to about 100at. % of silicon, which generally corresponds to Li_(4.4x)Si, where x isgreater than 0 to less than or equal to about 0.85. In other aspects,the precursor material optionally has greater than or equal to about 30atomic % to less than or equal to about 70 at. % of lithium andcorrespondingly greater than or equal to about 30 atomic % to less thanor equal to about 70 at. % of silicon, which generally corresponds toLi_(4.4x)Si, where x is greater than or equal to about 0.1 to less thanor equal to about 0.5. In yet other aspects, the precursor materialoptionally has about 50 at. % of lithium and correspondingly greaterthan or equal to about 50 at. % of silicon, which generally correspondsto Li_(4.4x)Si, where x is about 0.25.

In certain aspects, the lithium silicide alloy formed after thecentrifugal atomization process may comprise Li_(y)Si, where 0<y≤4.4) orin certain variations, Li_(4.4x)Si, where 0<x≤about 0.85. For example,the lithium silicide alloy formed after the centrifugal atomizationprocess may comprise one or more of the following phases: Li₂₂Si₅,Li₁₃Si₄, Li₇Si₃, Li₁₂Si₇, and LiSi. Notably, in certain variations wherea lower amount of lithium is present in the alloy, a phase comprisingonly Si may be present. In certain variations, the alloy may compriseone or more of the following phases: Li₂₂Si₅, Li₁₃Si₄, Li₇Si₃, Li₁₂Si₇,and LiSi. In addition to the lithium silicide alloy formed in thecentrifugal atomization process, the silicon oxide product may alsocomprise lithium silicates including Li₄SiO₄, Li₈SiO₆, Li₂SiO₃, and/orLi₂Si₂O₅, by way of example.

In certain aspects, a temperature in the centrifugal atomizing reactorduring centrifugal distribution of a molten precursor may be greaterthan or equal to 400° C. to less than or equal to about 1,000° C. Highertemperatures may be employed where the lithium, silicon, and oxygenprecursors are miscible, to facilitate formation of the desired phases.In certain variations, a temperature in the centrifugal atomizingreactor during centrifugal distribution of a molten precursor may begreater than or equal to 400° C. to less than or equal to about 800° C.Compared to other pre-lithiation methods, centrifugal/gas atomizationprovided by certain aspects of the present disclosure provides a meansto precisely control the extent of pre-lithiation and phases formed.

Thus, in various aspects, a centrifugal/gas atomizer reactor is used toproduce particles that comprise pre-lithiated silicon alloys, includinglithium silicide and lithium silicon oxides. Such a centrifugal/gasatomizer reactor provides high throughput production of lithium-siliconalloy electroactive particles having a relatively homogenous sizedistribution and thus, a high yield for a predetermined average particlesize diameter. The presence of Li_(4.4x)Si silicide alloy can reduce thelithium consumption and initial stress during formation cycles. This hasthe benefit of the electroactive material comprising silicon undergoingan initial volumetric expansion due to lithiation prior to beingincorporated into an electrode to enhance the mechanical properties ofthe electrode that is initially formed. Conventionally, theelectroactive material comprising silicon is incorporated into anelectrode (e.g., mixed in with the polymeric matrix and other electrodecomponents) and then lithiated where the initial expansion occurs. Thisexpansion upon lithiation can cause mechanical stress and potentialdamage to not only the electroactive particles, but also the surroundingcomposite. For a conventional silicon electroactive material, the extentof volumetric expansion that occurs during an initial lithiationreaction can cause the silicon particle to mechanically degrade andbreak into a plurality of smaller fragments or pieces. When the particlebreaks into smaller pieces, additional lithium is consumed to form newSEI and these fragments or smaller pieces can no longer maintainperformance of the electrochemical cell. When electroactive materialsare formed from the lithium and silicon alloys in accordance with thepresent disclosure, they have already undergone an initial volumetricexpansion and thus incorporating them into an electrode only causesminimal expansion and contraction stress during lithium cycling.

Moreover, the presence of lithium silicate (Li₄SiO₄) further enhancesthe mechanical properties of the lithium silicon oxide productcontaining lithium silicide alloys. As noted above, it physicallyretains the lithium silicide(s) in a silicon oxide material and furtherreduces overall volumetric expansion and contraction during lithiationcycling.

Furthermore, the lithium-silicon alloy powder created by thecentrifugal/gas atomization process can then be coated with one or morecoatings to protect the underlying electroactive material and/orincrease the electrical conductivity. Moreover, the lithium-siliconalloy particles can be exposed to a liquid electrolyte to form a surfacesolid electrolyte interface (SEI) layer before the electrode isfabricated.

An optional first coating is disposed over the surface of a negativeelectroactive material particle 100, like that shown in FIG. 3 . Incertain variations, a negative electroactive particle 100 having thecore region 110 comprising the lithium silicide (Li_(y)Si, where0<y≤4.4) and lithium silicate (Li₄SiO₄) and a first coating 120 may beincorporated into a negative electrode. However, in certain othervariations, a multilayered coating may be formed over the negativeelectroactive particle 100. Thus, a second coating 130 may be disposedover the first coating 120 and the core region 110. This negativeelectroactive particle having the multilayered coating including thefirst coating 120 and second coating 130 may be incorporated into anegative electrode. It should be noted that more than two layers ofcoatings may be applied or formed on the negative electroactive particle100.

In certain aspects, at least one of the first coating 120 or the secondcoating 130 may be an electrically conductive and ionically conductivelayer that comprises a carbon-containing or carbonaceous material. Incertain aspects, the electrically conductive and ionically conductivelayer may comprise an amorphous carbon that generally lacks anycrystalline structure or ordering. Amorphous carbon generally hassuperior mechanical properties, such as tensile strength, forwithstanding the volumetric changes of the electroactive material.Further, the electrically conductive and ionically conductive layer mayalso comprise a graphitic carbon, which is crystalline and has ordering.As will be described further below, graphitic carbon exhibits goodelectrical conductivity. Generally, the graphitic carbon may have ansp2/sp3 ratio of bonds ranging from about 70:30 to about 100:1. In anexample, the ratio of sp² carbon to sp³ carbon in the carbon coating maybe about 74 to about 26. Such an electrically conductive and ionicallyconductive layer can be formed in a pyrolysis process. In certainvariations, the amorphous carbon may form a first layer within the firstor second coatings 120, 130 and the graphitic carbon may form a secondlayer within the first or second coatings 120, 130. However, there maynot be a distinct compositional delineation between the layers, butrather a gradient region between the respective compositions thatdefines the coating. An outer region of the first or second coatings120, 130 may comprise graphitic carbon to provide good electricalconductivity, including good connection between adjacent electroactiveparticles.

Negative composite electrodes may comprise greater than or equal toabout 50% to less than or equal to about 90% of an electroactivematerial (e.g., lithium-silicon-oxide material comprising lithiumsilicide and lithium silicate particles optionally having one or morecoatings prepared in accordance with the present disclosure), optionallygreater than or equal to about 5% to less than or equal to about 30% ofan electrically conductive material, and a balance binder. Electricallyconductive materials are well known in the art and include graphite,carbon black, carbon nanotubes, powdered nickel, conductive metalparticles, conductive polymers, and combinations thereof. Useful bindersinclude any of those described above. For example, useful binders maycomprise a polymeric material and extractable plasticizer suitable forforming a bound porous composite, such as halogenated hydrocarbonpolymers (such as poly(vinylidene chloride) andpoly((dichloro-1,4-phenylene)ethylene), fluorinated urethanes,fluorinated epoxides, fluorinated acrylics, copolymers of halogenatedhydrocarbon polymers, epoxides, ethylene propylene diamine termonomer(EPDM), ethylene propylene diamine termonomer (EPDM), polyvinylidenedifluoride (PVDF), hexafluoropropylene (HFP), ethylene acrylic acidcopolymer (EAA), ethylene vinyl acetate copolymer (EVA), EAA/EVAcopolymers, PVDF/HFP copolymers, carboxy methyl cellulose (CMC), styrenebutyl rubber (SBR), and mixtures thereof.

An electrode may be made by mixing the electrode active material, suchas coated lithium-silicon oxide material containing powder or particles,into a slurry with a polymeric binder compound, a non-aqueous solvent,optionally a plasticizer, and optionally if necessary, electricallyconductive particles. The slurry can be mixed or agitated, and thenthinly applied to a substrate via a doctor blade. The substrate can be aremovable substrate or alternatively a functional substrate, such as acurrent collector (such as a metallic grid or mesh layer) attached toone side of the electrode film. In one variation, heat or radiation canbe applied to evaporate the solvent from the electrode film, leaving asolid residue. The electrode film may be further consolidated, whereheat and pressure are applied to the film to sinter and calendar it. Inother variations, the film may be air-dried at moderate temperature toform self-supporting films. If the substrate is removable, then it isremoved from the electrode film that is then further laminated to acurrent collector. With either type of substrate, it may be necessary toextract or remove the remaining plasticizer prior to incorporation intothe battery cell.

A battery may thus be assembled in a laminated cell structure,comprising an anode layer, a cathode layer, and electrolyte/separatorbetween the anode and cathode layers. The anode and cathode layers eachcomprise a current collector. A negative anode current collector may bea copper collector foil, which may be in the form of an open mesh gridor a thin film. The current collector can be connected to an externalcurrent collector tab.

For example, in certain variations, an electrode membrane, such as ananode membrane, comprises the electrode active material (e.g., coatedlithium-silicon-oxide containing particles) dispersed in a polymericbinder matrix over a current collector. The separator can then bepositioned over the negative electrode element, which is covered with apositive electrode membrane comprising a composition of a finely dividedlithium insertion compound in a polymeric binder matrix. A positivecurrent collector, such as aluminum collector foil or grid completes theassembly. Tabs of the current collector elements form respectiveterminals for the battery. A protective bagging material covers the celland prevents infiltration of air and moisture. Into this bag, a liquidelectrolyte may be injected into the separator (and may be imbibed intothe positive and/or negative electrodes) suitable for lithium iontransport. In certain aspects, the laminated battery is furtherhermetically sealed prior to use.

A surface coating (such as an oxide-based coating) applied to a negativeelectroactive material comprising a lithium-silicon-oxide composition inaccordance with certain aspects of the present technology may be formedover the entire exposed surface and thus serve as an artificial solidelectrolyte interface layer, which can protect the electrode fromreaction with liquid electrolyte. In various aspects, the electroactivematerials comprising lithium-silicon-oxide compositions may have asurface coating providing certain advantages, such as high cut voltage(e.g., cut-off potentials relative to a lithium metal referencepotential) that desirably minimizes or avoids SEI formation. In certainaspects, a lithium-ion battery incorporating an inventive negativeelectroactive material having a lithium-silicon-oxide compositionselectroactive material with optional coating(s) substantially maintainscharge capacity (e.g., performs within a preselected range or othertargeted high capacity use) for at least about 1,000 hours of batteryoperation, optionally greater than or equal to about 1,500 hours ofbattery operation, optionally greater than or equal to about 2,500 hoursor longer of battery operation, and in certain aspects, optionallygreater than or equal to about 5,000 hours or longer (active cycling).

In certain aspects, the lithium-ion battery incorporating an inventivenegative electroactive/electrode material having a lithium-silicon-oxidecomposition electroactive material with optional coating(s) maintainscharge capacity and thus is capable of operating within 20% of targetcharge capacity for a duration of greater than or equal to about 2 years(including storage at ambient conditions and active cycling time),optionally greater than or equal to about 3 years, optionally greaterthan or equal to about 4 years, optionally greater than or equal toabout 5 years, optionally greater than or equal to about 6 years,optionally greater than or equal to about 7 years, optionally greaterthan or equal to about 8 years, optionally greater than or equal toabout 9 years, and in certain aspects, optionally greater than or equalto about 10 years.

In other aspects, the lithium-ion battery incorporating an inventiveelectroactive material is capable of operating at less than or equal toabout 30% change in a preselected target charge capacity (thus having aminimal charge capacity fade), optionally at less than or equal to about20%, optionally at less than or equal to about 15%, optionally at lessthan or equal to about 10%, and in certain variations optionally at lessthan or equal to about 5% change in charge capacity for a duration of atleast about 100 deep discharge cycles, optionally at least about 200deep discharge cycles, optionally at least about 500 deep dischargecycles, optionally at least about 1,000 deep discharge cycles.

Stated in another way, in certain aspects, a lithium-ion battery orelectrochemical cell incorporating the inventive negative electroactivematerial having a lithium-silicon-oxide electroactive material withoptional coating(s) substantially maintains charge capacity and iscapable of operation for at least about 1,000 deep discharge cycles,optionally greater than or equal to about 2,000 deep discharge cycles,optionally greater than or equal to about 3,000 deep discharge cycles,optionally greater than or equal to about 4,000 deep discharge cycles,and in certain variations, optionally greater than or equal to about5,000 deep discharge cycles.

The present disclosure thus contemplates methods of forming thecarbon-containing coatings and/or oxide-containing coatings on thenegative electroactive materials comprising lithium-silicon-oxidematerials. The carbon-containing coating can be formed in a pyrolysisprocess where a hydrocarbon is reduced to form a carbonaceous coating.The process for applying the oxide-based surface coating may be selectedfrom a group consisting of atomic layer deposition (ALD), chemical vaporinfiltration, chemical vapor deposition, physical vapor deposition, wetchemistry, and any combinations thereof. Indeed, in certain aspects, adeposition process may first comprise applying a carbon material to oneor more surfaces of the electrode material by a first process, followedby applying a metal oxide material in a second process, or vice versa.Furthermore, in certain variations, a first coating may comprise anoxide-based coating, a second coating may comprise a carbon-basedcoating, and a third coating may comprise an oxide-based coating.

In certain aspects, the first and second processes may be in the sametype of process or equipment, but the deposition or applying steps arecarried out separately (e.g., sequentially) as described in U.S. PatentPublication No. 2021/0175491 entitled “Methods of Forming PrelithiatedSilicon Alloy Electroactive Materials,” the relevant portions of whichare incorporated herein by reference. As will be described furtherherein, the first and second coating processes may be conducted indownstream reaction chambers in fluid communication with the centrifugalatomization reactor. In other aspects, the first and second processesmay be entirely distinct from one another and/or further conductedseparately after the formation of the negative electroactivelithium-silicon oxide material particles in the centrifugal atomizationreactor.

The present disclosure thus contemplates methods of forming thecarbon-containing coatings and/or oxide-containing coatings on thenegative electroactive materials comprising lithium-silicon alloys. Thecarbon-containing coating can be formed in a pyrolysis process where ahydrocarbon is reduced to form a carbonaceous coating. The process forapplying the oxide-based surface coating may be selected from a groupconsisting of atomic layer deposition (ALD), chemical vaporinfiltration, chemical vapor deposition, physical vapor deposition, wetchemistry, and any combinations thereof. Indeed, in certain aspects, adeposition process may first comprise applying a carbon material to oneor more surfaces of the electrode material by a first process, followedby applying a metal oxide material in a second process, or vice versa.Furthermore, in certain variations, a first coating may comprise anoxide-based coating, a second coating may comprise a carbon-basedcoating, and a third coating may comprise an oxide-based coating.

In certain aspects, the first and second processes may be in the sametype of process or equipment, but the deposition or applying steps arecarried out separately (e.g., sequentially). As will be describedfurther herein, the first and second coating processes may be conductedin downstream reaction chambers in fluid communication with thecentrifugal atomization reactor. In other aspects, the first and secondprocesses may be entirely distinct from one another and/or furtherconducted separately after the formation of the negative electroactivelithium-silicon alloy particles in the centrifugal atomization reactor.

The foregoing description of the embodiments has been provided forpurposes of illustration and description. It is not intended to beexhaustive or to limit the disclosure. Individual elements or featuresof a particular embodiment are generally not limited to that particularembodiment, but, where applicable, are interchangeable and can be usedin a selected embodiment, even if not specifically shown or described.The same may also be varied in many ways. Such variations are not to beregarded as a departure from the disclosure, and all such modificationsare intended to be included within the scope of the disclosure.

What is claimed is:
 1. A method of making a negative electrode materialfor an electrochemical cell that cycles lithium ions, the methodcomprising: centrifugally distributing a molten precursor comprisingsilicon, oxygen, and lithium by contacting the molten precursor with arotating surface in a centrifugal atomizing reactor and solidifying themolten precursor to form a plurality of substantially round solidelectroactive particles comprising a mixture of lithium silicide(Li_(y)Si, where 0<y≤4.4) and a lithium silicate (Li₄SiO₄) and having aD50 diameter of less than or equal to about 20 micrometers, wherein atemperature in the centrifugal atomizing reactor is greater than orequal to 400° C. to less than or equal to about 800° C. during thecentrifugally distributing.
 2. The method of claim 1, wherein the moltenprecursor is formed by melting a precursor comprising silicon (Si) andlithium oxide (Li₂O).
 3. The method of claim 2, wherein the precursorcomprises a mole ratio of silicon (Si) to lithium oxide (Li₂O) ofgreater than or equal to about 1:2 to less than or equal to about 2:1.4. The method of claim 2, wherein the precursor further comprisessilicon dioxide (SiO₂).
 5. The method of claim 1, wherein the lithiumsilicide is further represented by the formula Li_(4.4x)Si, where x isgreater than 0 and less than or equal to about 0.85.
 6. The method ofclaim 1, wherein the plurality of substantially round solidelectroactive particles comprise a coating selected from the groupconsisting of: carbon-containing coatings, oxide-containing coatings,and combinations thereof.
 7. The method of claim 1, wherein anenvironment in the centrifugal atomizing reactor has less than or equalto about 0.5% by weight of any oxygen-bearing species.
 8. The method ofclaim 1, wherein a flow rate of the centrifugal atomizing reactor isgreater than or equal to 50 kg/hour to less than or equal to about 500kg/hour.
 9. The method of claim 1, wherein the D50 diameter is greaterthan or equal to about 1 μm to less than or equal to about 10 μm. 10.The method of claim 1, wherein the plurality of substantially roundsolid electroactive particles has a polydispersity index of less than orequal to about 1.2.
 11. A method of making a negative electrode materialfor an electrochemical cell that cycles lithium ions, the methodcomprising: centrifugally distributing a molten precursor by contactingthe molten precursor with a rotating surface in a centrifugal atomizingreactor, wherein the molten precursor is formed from a mixturecomprising silicon dioxide (SiO₂), lithium oxide (Li₂O), and silicon(Si); and solidifying the molten precursor to form a plurality ofsubstantially round solid electroactive particles comprising a mixtureof lithium silicide (Li_(y)Si, where 0<y≤4.4) and a lithium silicate(Li₄SiO₄) and having a D50 diameter of less than or equal to about 20micrometers.
 12. The method of claim 11, wherein the mixture comprises amole ratio of silicon (Si) to lithium oxide (Li₂O) of greater than orequal to about 1:2 to less than or equal to about 2:1.
 13. The method ofclaim 11, wherein the lithium silicide is further represented by theformula Li_(4.4x)Si, where x is greater than 0 and less than or equal toabout 0.85.
 14. The method of claim 11, wherein a temperature in thecentrifugal atomizing reactor is greater than or equal to 400° C. toless than or equal to about 800° C. during the centrifugallydistributing.
 15. The method of claim 11, wherein a flow rate of thecentrifugal atomizing reactor is greater than or equal to 50 kg/hour toless than or equal to about 500 kg/hour.
 16. The method of claim 11,wherein the D50 diameter is greater than or equal to about 1 μm to lessthan or equal to about 10 μm.
 17. The method of claim 11, wherein theplurality of substantially round solid electroactive particles has apolydispersity index of less than or equal to about 1.2.
 18. A method ofmaking a negative electrode material for an electrochemical cell thatcycles lithium ions, the method comprising: melting a precursor mixturecomprising lithium oxide (Li₂O) and silicon (Si) to form a moltenprecursor; centrifugally distributing the molten precursor by contactingthe molten precursor with a rotating surface in a centrifugal atomizingreactor; and solidifying the molten precursor to form a plurality ofsubstantially round solid electroactive particles comprising lithiumsilicide (Li_(y)Si, where 0<y≤4.4) and a lithium silicate (Li₄SiO₄) andhaving a D50 diameter of less than or equal to about 20 micrometers. 19.The method of claim 18, wherein the precursor mixture further comprisessilicon dioxide (SiO₂).